POLYODONTIDA. — XX. oO 
guish the living Ganoids from all Teleosts, but none of these char- 
acters can be verified in the extinct forms. It seems to us better 
not to regard the Ganoids as a separate class or subclass, but to 
unite them with the Teleosts. (yavos, splendor, from the enam- 
elled scales.) 
OrverR VII. SELACHOSTOMI. 
This order contains but one family. (oédaxos, shark or other 
cartilaginous fish; ordéua, mouth.) 
Famity XX. POLYODONTIDA). (THe Pappte- 
FISHES.) 
Body fusiform, the skin mostly smooth; snout prolonged in a 
flat, spatulate blade, which overhangs the broad, terminal mouth ; 
the “spatula” with a reticulated framework; teeth very numerous, 
minute, disappearing with age; opercle rudimentary, its skin pro- 
duced in a long flap; gills 43; no pseudobranchie; gill rakers very 
long, in two rows, separated by membrane; gill membranes con- 
nected, free from isthmus; one branchiostegal; spiracles present. 
C. fin with fulera; D. posterior; tail heterocercal, the lower lobe 
nearly as long as the upper; sides of tail with rhombic plates; 
air-bladder large, cellular; stomach cecal, the pyloric ceca form- 
ing a branching, leaf-like organ. Singular fishes, feeding on mud 
and minute organisms which they stir up on the bottom with the 
leng oar-like snout. Two species, Psephurus gladius of rivers of 
China, and the following. 
a. Gill rakers very fine and numerous; caudal fulcra many, small. 
PoLyopDon, 29. 
29. POLYODON (Lacépede) Bloch & Schneider. 
(woAvs, many; ddav, tooth.) 
39. P. spathula (Walbaum). Papp e-Fisu. Spoon-BItt. 
Duck-Bittep Cat. Olivaceous; opercular flap in adult reaching 
V.; head with flap and spatula more than half length. D. 55, 
A. 57, V.45. L. 6 feet. Miss. valley; common in larger streams. 
(P. folium Lac.) (Lat. spatula.) 
Orver VIIL GLANIOSTOMI. 
This order contains only the family of Sturgeons. (yAdus, cat- 
fish ; ordua, mouth.) 
Famity XXI. ACIPENSERIDA. (Tue Sturceons.) 
Body elongate, fusiform, with five rows of bony keeled shields, 
the skin between these rows with small or minute plates; snout 
produced; mouth inferior, protractile, toothless; four barbels in a 
cross-row before mouth; gills 4; an accessory opercular gill; no 
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